1. Field of the Invention
The present invention relates to a disk drive, and more particularly, to an actuator latch system for a disk drive, in which an actuator is locked in a predetermined position when a disk is not rotating, such that the actuator is prevented from arbitrarily rotating due to an impact.
2. Description of the Related Art
As a data storage device of a computer, a hard disk drive (HDD) is a device for reproducing/recording data from/on a disk using a read/write head. In such an HDD, a head moves to a desired position by motion of an actuator, while being lifted above a recording surface of a rotating disk, and executes the reproducing/recording functions.
Meanwhile, if the HDD does not operate, that is, if the disk is not rotating, the head is parked off the recording surface of the disk to prevent a collision with the recording surface of the disk. Such head parking systems can be classified into a contact start-stop (CSS) system and a ramp loading system. In the CSS system, a parking zone, in which data is non-recordable, is provided in an inner circumference of the disk and the head is parked in contact with the parking zone. In the ramp loading system, the head is parked on a ramp, which is installed outside the disk.
In a state with the head parked on the parking zone or the ramp, the actuator may arbitrarily rotate due to an impact or vibration, such that the head is forced out of the parking zone or the ramp and onto the recording surface of the disk. In this case, the head makes contact with the recording surface of the disk, such that the head and/or the recording surface may be damaged. Therefore, when the head is parked on the parking zone or the ramp, the actuator must be locked to a predetermined position so that it cannot rotate arbitrarily. For this purpose, various kinds of actuator latch systems are provided in the HDD.
FIG. 1 illustrates a prior art actuator latch apparatus for a HDD, which is disclosed in U.S. Pat. No. 5,448,436.
Referring to FIG. 1, an HDD includes an actuator 20 to move a read/write head to a predetermined position on the disk. The actuator 20 includes a swing arm 22 rotatably mounted on a pivot 21, which is installed in a base member 10, and a suspension 23 installed in one end portion of the swing arm 22 to elastically bias the slider 24 toward a surface of the disk 14. A head is mounted on the slider 24.
The HDD further includes an inertial latch apparatus 50 that locks the actuator 20 when the head is parked in a ramp 30. The inertial latch apparatus 50 includes a latch arm 51 rotating due to an inertia, a latch hook 52 installed on a front end of the latch arm 51, a notch 27 provided at a rear end of the swing arm 22, a crash stop 40 limiting a clockwise rotation of the swing arm 22, and a latch stop 53 limiting a clockwise rotation of the latch arm 51.
In the inertial latch apparatus 50, if a rotational force impacts the HDD in a clockwise direction, the swing arm 22 and the latch arm 51 rotate in a counterclockwise direction due to inertia. Thus, the latch hook 52 is caught by the notch 27, such that the swing arm 22 cannot rotate further.
On the other hand, if a rotational force impacts the HDD in a counterclockwise direction, the swing arm 22 and the latch arm 51 rotate in a clockwise direction due to inertia. At first, the swing arm 22 rotates in a clockwise direction, but it collides with the crash stop 40 and rebounds from the crash stop 40, resulting in the swing arm 22 rotating in a counterclockwise direction. The latch arm 51 collides with the latch stop 53 and rebounds from the latch stop 53, resulting in the latch arm 51 rotating in a counterclockwise direction. Since the swing arm 22 and the latch arm 51 rotate in the counterclockwise direction due to the rebound, the latch hook 52 is engaged with the notch 27, thereby locking the actuator 20. An O-ring 41 is installed in the crash stop 40 which makes the swing arm 22 rebound easily. Also, an O-ring 57 is installed in the latch stop 53 and the latch arm 51 is made of elastic material, thus making the latch arm 51 rebound easily.
The inertial latch apparatus 50 operates by a relatively strong rotational impact force which results in the rotation of the latch arm 51. If a relatively weak rotational impact force is applied the HDD, the latch arm 51 does not rotate, and thus the actuator 20 is not locked. As a result, the actuator 20 rotates arbitrarily. In other words, when a relatively weak impact force is applied, the inertial latch apparatus 50 has a drawback in that a locking reliability of the actuator 20 cannot be guaranteed.
FIGS. 2A and 2B illustrate an improvement of the prior art actuator latch apparatus.
Referring to FIG. 2A, an actuator 60 includes a voice coil motor (VCM) rotating a swing arm 62. The VCM includes a VCM coil 67 coupled to a rear end portion of the swing arm 62, and a magnet 68 arranged to face the VCM coil 67. The magnet 68 is supported by a yoke 69.
An actuator latch apparatus 80 of FIGS. 2A and 2B has a structure that can lock the actuator 60 using a magnetic force of the magnet 68 as well as inertia. The actuator latch apparatus 80 includes a notch 81, which is provided at an end portion of the swing arm 62, and a latch lever 83, which may rotate around a latch pivot 84. A first core 82 is provided at a rear end portion of the swing arm 62, such that a magnetic force acts between the first core 82 and the swing arm 62. The first core 82 generates a torque that causes the swing arm 62 to rotate in a clockwise direction by a magnetic force of the magnet 68. The latch lever 83 has a hook 85 at a first end portion and a second core 86 at a second end portion. The hook 85 is caught by the notch 81, and a magnetic force acts between the second core 86 and the magnet 68. The second core 86 generates a torque to rotate the latch lever 83 in a clockwise direction due to a magnetic force of the magnet 68. A clockwise angular displacement of the latch lever 83 is limited by a latch stop 89.
An operation of the latch apparatus 80 will now be described. When a head mounted on a slider 64 is parked on a ramp 70, the VCM rotates the swing arm 62 around a pivot 61 in a clockwise direction. A rear portion of the swing arm 62 is in contact with a protrusion 88, which is provided at the other end portion of the latch lever 83. Thus, the latch lever 83 rotates in a counterclockwise direction. While the latch lever 83 rotates in a counterclockwise direction, if a protrusion 87 provided at the first end portion of the latch lever 83 is in contact with the swing arm 62, the clockwise rotation of the swing arm 62 is stopped, as is the counterclockwise rotation of the latch lever 83. In this manner, the latch lever 83 also acts as a crash stop to limit the clockwise angular displacement of the swing arm 62. As is shown in FIG. 2A, parking of the head is completed and the latch apparatus 80 locks the actuator 60 simultaneously. At this point, the magnetic force acting between the first core 82 and the magnet 68 is set to be greater than that acting between the second core 86 and the magnet 68, such that the locking state of the actuator 60 is maintained.
If a clockwise rotational impact force is greater than the magnetic force existing between the first core 82 and the magnet 68, and is applied to the HDD when the head is in the parked state, the swing arm 62 and the latch lever 83 rotate in the counterclockwise direction due to inertia. Thus, the hook 85 of the latch lever 83 is caught by the notch 81, such that the swing arm 62 cannot rotate further.
On the other hand, if a counterclockwise rotational impact force is applied to the HDD, clockwise inertia acts between the swing arm 62 and the latch lever 83. Accordingly, the swing arm 62 and the latch lever 83 collide with each other and then rebound, such that both the swing arm 62 and the latch lever 83 rotate in a counterclockwise direction. As is shown in FIG. 2A, since the swing arm 62 and the latch lever 83 are in contact with each other, the counterclockwise torque of the swing arm 62 due to the rebound is weak. Therefore, the counterclockwise rotation of the swing arm 62 does not occur, due to the magnetic force acting between the first core 82 and the magnet 68.
If a rotational impact force is less than the magnetic force between the first core 82 and the magnet 68, and is applied to the HDD, the rotation of the swing arm 62 does not occur due to the magnetic force.
In this manner, the actuator latch apparatus 80 uses the magnetic force and inertia in combination, so that the actuator 60 is reliably locked in the event of a relatively weak impact and vibration as well as a strong impact.
Referring to FIG. 2B, when the HDD operates, the head must move from the ramp 70 to the recording surface of the disk. For this, the locking state of the actuator 60 must be released. If power is supplied to the VCM coil 67, the swing arm 62 rotates in a counterclockwise direction with a resistance to the magnetic force of the magnet 68 acting on the first core 82 of the swing arm 62. Simultaneously, the latch lever 83 rotates in a clockwise direction due to the magnetic force of the magnet 68 acting on the second core 86, such that the notch 81 of the swing arm 62 does not interfere with the hook 85 of the latch lever 83.
In the actuator latch apparatus 80, when the swing arm 62 rotates in a clockwise direction to park the head in the ramp 70, the swing arm 62 contacts with the protrusions 87 and 88 of the latch lever 83. At this time, a large impact force is applied to the protrusions 87 and 88 of the latch lever 83. Such an impact produces great noises. Also, the impact force is transferred to the head through the swing arm 62, such that the head may be damaged or read/write performance may be degraded. Due to the impact, the protrusions 87 and 88 of the latch lever 83 are abraded, thus generating particles. These particles cause the head and the disc surface to be contaminated or damaged.